Fuel-dispensing nozzles normally include a shutoff system for automatically stopping the flow of fuel into the container being filled when the level of fuel in the container reaches a predetermined level. In service station operations where the discharge spout of the fuel nozzle is inserted into the fill pipe of a vehicle fuel tank, the fuel nozzle is normally arranged to be manually latched in an open position and to automatically close when the fuel tank is substantially filled.
Nozzle automatic fuel shutoff systems used heretofore have incorporated some sort of vacuum-operated mechanism to automatically close the nozzle flow control valve when normal venting of the vacuum mechanism by way of a vent tube is interrupted. In these arrangements, the vent tube extends from the vacuum mechanism in the nozzle main body portion and through the discharge spout of the fuel nozzle to a vent passage opening at the outlet end of the discharge spout. When the level of fuel in the tank being filled rises to a level sufficient to block the vent passage opening, the vacuum mechanism is actuated to close the flow control valve. With the flow control valve closed, the flow of fuel through the nozzle is stopped. Examples of these vacuum-operated shutoff systems may be found in U.S. Pat. No. 4,142,562, U.S. Pat. No. 4,131,140, U.S. Pat. No. 4,058,149, and U.S. Pat. No. 3,176,980.
The vacuum-operated shutoff systems are fairly complicated mechanical arrangements, and as such, present manufacture and maintenance problems. On the other hand, the present invention offers a relatively simple automatic fuel shutoff system which greatly reduces the number of moving parts that have to be built into any particular fuel nozzle. Thus, this system is relatively inexpensive to build and maintain.